Comparison of PET/MRI and PET/CT studies in liver selective internal radiation therapy with 90Y microspheres

1450 Objectives The aim of our study was to compare the distribution of 90Y microspheres obtained from PET/MRI and PET/CT in post-therapy studies, in liver Selective Internal Radiation Therapy (SIRT). Methods In a continuing study after SIRT with 90Y microspheres, patients were imaged on a 4R, 40 slice PET/CT system (Siemens mCT). The low mA, non-diagnostic CT images were used for attenuation correction and localization of the 90Y microspheres in the PET/CT studies. The acquisition time was 15 min. Immediately after PET/CT study, in an adjacent room a PET/MRI study was done on a Siemens mMR system. The acquisition time was 20 min, and attenuation correction was done using the scanner standard 4 segment (air, soft tissue, lung, and fat) MR based attenuation map. In both studies, the 22Na isotope was selected, because neither systems has 90Y in their database. The data were reconstructed using the vendor’s reconstruction software and were transferred to a common platform where the PET/MRI and PET/CT 90Y microspheres liver distributions were visually compared. Results The distributions of 90Y microspheres obtained from PET/MRI and PET/CT in post-therapy studies were very similar. PET images from the PET/MRI system were slightly noisier and lower in quantification than that from the PET/CT system. However, the PET/MRI study provided different MRI sequences for anatomical reference including T2 HASTE and T1 VIBE. In the future we will optimize MRI sequences for 90Y liver selective internal radiation therapy. Conclusions Our results indicated that in liver selective internal radiation therapy with 90Y microspheres, the final administrated 90Y distribution can be adequately imaged by PET/CT and PET/MRI state-of-the-art systems.